The present invention relates to a vaccine for the treatment of porcine reproductive and respiratory syndrome (PRRS).
In 1987, the swine-producing industry in the United States experienced an unknown infectious disease which had a serious economic impact on the swine industry. The disease syndrome was reported in Europe including Germany, Belgium, the Netherlands, Spain and England.
The disease is characterized by reproductive failure, respiratory disease and various clinical signs including loss of appetite, fever, dyspnea, and mild neurologic signs. A major component of the syndrome is reproductive failure which manifests itself as premature births, late term abortions, pigs born weak, stillbirths, mummified fetuses, decreased farrowing rates, and delayed return of estrus. Clinical signs of respiratory disease are most pronounced in pigs under 3-weeks-of-age but are reported to occur in pigs at all stages of production. Affected piglets grow slowly, have roughened hair coats, respiratory distress ("thumping"), and increased mortality.
The disease syndrome has been referred to by many different terms including mystery swine disease (MSD), porcine epidemic abortion and respiratory syndrome (PEARS), swine infertility and respiratory syndrome (SIRS). The name now commonly used is porcine reproductive and respiratory syndrome (PRRS); this term will be employed throughout this patent application.
It is an object of the invention to provide a vaccine which protects a pig against clinical disease caused by PRRS. Another object is to provide a vaccine which, when administered to a breeding swine herd, will reduce the presence of PRRS in their population.